System and method for multilevel scheduling

ABSTRACT

A method and apparatus for determining multilevel scheduling of a reverse link communication. An embodiment includes estimating capacity on the reverse link based on the sector load. An embodiment includes estimating load contribution based on an estimated signal-to-noise ratio. An embodiment includes estimating capacity available to schedule based on a ratio of measured other-cell interference over thermal noise, and based on sector load. An embodiment includes a method of distributing sector capacity across a base station (BS) and a base station controller (BSC). An embodiment includes determining priority of a station based on the pilot energy over noise plus interference ratio, the soft handoff factor, the fairness value, and the fairness factor α.

[0001] The present application for Patent claims priority of U.S.Provisional Application No. 60/409,820, filed Sep. 10, 2002, assigned tothe assignee hereof and hereby expressly incorporated by referenceherein.

[0002] Reference to Co-Pending Applications for Patent

[0003] The present invention is related to the following Applicationsfor Patent in the U.S. Patent & Trademark Office:

[0004] “System and Method for Rate Assignment” by Avinash Jain, havingAttorney Docket No. (020713U1), filed concurrently herewith and assignedto the assignee hereof, and which is expressly incorporated by referenceherein.

BACKGROUND

[0005] 1. Field

[0006] The present disclosed embodiments relate generally to wirelesscommunications, and more specifically to reverse link rate scheduling ina communication system having a variable data transmission rate.

[0007] 2. Background

[0008] The field of communications has many applications including,e.g., paging, wireless local loops, Internet telephony, and satellitecommunication systems. An exemplary application is a cellular telephonesystem for mobile subscribers. (As used herein, the term “cellular”system encompasses both cellular and personal communications services(PCS) system frequencies.) Modern communication systems designed toallow multiple users to access a common communications medium have beendeveloped for such cellular systems. These modern communication systemsmay be based on code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA), spacedivision multiple access (SDMA), polarization division multiple access(PDMA), or other modulation techniques known in the art. Thesemodulation techniques demodulate signals received from multiple users ofa communication system, thereby enabling an increase in the capacity ofthe communication system. In connection therewith, various wirelesssystems have been established including, e.g., Advanced Mobile PhoneService (AMPS), Global System for Mobile communication (GSM), and someother wireless systems.

[0009] In FDMA systems, the total frequency spectrum is divided into anumber of smaller sub-bands and each user is given its own sub-band toaccess the communication medium. Alternatively, in TDMA systems, eachuser is given the entire frequency spectrum during periodicallyrecurring time slots. A CDMA system provides potential advantages overother types of systems, including increased system capacity. In CDMAsystems, each user is given the entire frequency spectrum for all of thetime, but distinguishes its transmission through the use of a uniquecode.

[0010] A CDMA system may be designed to support one or more CDMAstandards such as (1) the “TIA/EIA-95-B Mobile Station-Base StationCompatibility Standard for Dual-Mode Wideband Spread Spectrum CellularSystem” (the IS-95 standard), (2) the standard offered by a consortiumnamed “3rd Generation Partnership Project” (3GPP) and embodied in a setof documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS25.213, and 3G TS 25.214 (the W-CDMA standard), (3) the standard offeredby a consortium named “3rd Generation Partnership Project 2” (3GPP2) andembodied in “TR-45.5 Physical Layer Standard for cdma2000 SpreadSpectrum Systems” (the IS-2000 standard), and (4) some other standards.

[0011] In the above named CDMA communication systems and standards, theavailable spectrum is shared simultaneously among a number of users, andtechniques such as soft handoff are employed to maintain sufficientquality to support delay-sensitive services, such as voice. Dataservices are also available. More recently, systems have been proposedthat enhance the capacity for data services by using higher ordermodulation, very fast feedback of Carrier to Interference ratio (C/I)from a mobile station, very fast scheduling, and scheduling for servicesthat have more relaxed delay requirements. An example of such adata-only communication system using these techniques, is the high datarate (HDR) system that conforms to the TIA/EIA/IS-856 standard (theIS-856 standard).

[0012] In contrast to the other above named standards, an IS-856 systemuses the entire spectrum available in each cell to transmit data to asingle user at one time. One factor used in determining which user isserved is link quality. By using link quality as a factor for selectingwhich user is served, the system spends a greater percentage of timesending data at higher rates when the channel is good, and therebyavoids committing resources to support transmission at inefficientrates. The net effect is higher data capacity, higher peak data rates,and higher average throughput.

[0013] Systems can incorporate support for delay-sensitive data, such asvoice channels or data channels supported in the IS-2000 standard, alongwith support for packet data services such as those described in theIS-856 standard. One such system is described in a proposal submitted byLG Electronics, LSI Logic, Lucent Technologies, Nortel Networks,QUALCOMM Incorporated, and Samsung to the 3rd Generation PartnershipProject 2 (3GPP2). The proposal is detailed in documents entitled“Updated Joint Physical Layer Proposal for 1xEV-DV”, submitted to 3GPP2as document number C50-20010611-009, Jun. 11, 2001; “Results of L3NQSSimulation Study”, submitted to 3GPP2 as document numberC50-20010820-011, Aug. 20, 2001; and “System Simulation Results for theL3NQS Framework Proposal for cdma2000 1x-EVDV”, submitted to 3GPP2 asdocument number C50-20010820-012, Aug. 20, 2001. These are hereinafterreferred to as the 1xEV-DV proposal.

[0014] Multi-level scheduling may be useful for more efficient capacityutilization on the reverse link.

SUMMARY

[0015] Embodiments disclosed herein address the above stated needs byproviding a method and system for multilevel scheduling for rateassignment in a communication system.

[0016] In an aspect, a method for estimating capacity used on a reverselink, comprises measuring a plurality of signal-to-noise ratios at astation for a plurality of rates, determining sector load based on themeasured plurality of signal-to-noise ratios, an assigned transmissionrate, and an expected transmission rate, and estimating capacity on thereverse link based on the sector load.

[0017] In an aspect, a method of estimating load contribution to asector antenna, comprises assigning a transmission rate Ri on a firstcommunication channel, determining an expected rate of transmission E[R]on a second communication channel, estimating a signal-to-noise ratio ofa station for the assigned transmission rate Ri on the firstcommunication channel and the expected rate of transmission E[R] on asecond communication channel, and estimating the load contribution basedon the estimated signal-to-noise ratio.

[0018] In an aspect, a method for estimating capacity available toschedule, comprises measuring other-cell interference during a previoustransmission (I_(oc)), determining thermal noise (N_(o)), determiningsector load (Load_(j)), and determining rise-over-thermal (ROT_(j))based on the ratio of the measured other-cell interference over thermalnoise, and based on the sector load.

[0019] In another aspect, a method of distributing sector capacityacross a base station (BS) and a base station controller (BSC),comprises measuring other-cell interference during a previoustransmission (I_(oc)), determining thermal noise (N_(o)), determining amaximum rise-over-thermal (ROT(max)), determining an estimated assignedload at the BSC (Load_(j)(BSC)), and determining a sector capacitydistributed to the base station based on the ratio of the measuredother-cell interference over thermal noise, the maximumrise-over-thermal, and the estimated assigned load at the BSC.

[0020] In yet another aspect, a method of determining priority of astation, comprises determining pilot energy over noise plus interferenceratio (Ecp/Nt), determining a soft handoff factor (SHOfactor),determining a fairness value (F), determining a proportional fairnessvalue (PF), determining a fairness factor α, and determining a maximumcapacity utilization based on the pilot energy over noise plusinterference ratio, the soft handoff factor, the fairness value, and thefairness factor α.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 exemplifies an embodiment of a wireless communicationsystem with three mobile stations and two base stations;

[0022]FIG. 2 shows set point adjustment due to rate transitions on R-SCHin accordance with an embodiment.

[0023]FIG. 3 shows scheduling delay timing in accordance with anembodiment;

[0024]FIG. 4 shows parameters associated in mobile station scheduling ona reverse link;

[0025]FIG. 5 is a flowchart of a scheduling process in accordance withan embodiment;

[0026]FIG. 6 is a block diagram of a base station in accordance with anembodiment; and

[0027]FIG. 7 is a block diagram of a mobile station in accordance withan embodiment.

DETAILED DESCRIPTION

[0028] The word “exemplary” is used herein to mean “serving as anexample, instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments.

[0029] A wireless communication system may comprise multiple mobilestations and multiple base stations. FIG. 1 exemplifies an embodiment ofa wireless communication system with three mobile stations 10A, 10B and10C and two base stations 12. In FIG. 1, the three mobile stations areshown as a mobile telephone unit installed in a car 10A, a portablecomputer remote 10B, and a fixed location unit 10C such as might befound in a wireless local loop or meter reading system. Mobile stationsmay be any type of communication unit such as, for example, hand-heldpersonal communication system units, portable data units such as apersonal data assistant, or fixed location data units such as meterreading equipment. FIG. 1 shows a forward link 14 from the base station12 to the mobile stations 10 and a reverse link 16 from the mobilestations 10 to the base stations 12.

[0030] As a mobile station moves through the physical environment, thenumber of signal paths and the strength of the signals on these pathsvary constantly, both as received at the mobile station and as receivedat the base station. Therefore, a receiver in an embodiment uses aspecial processing element called a searcher element, that continuallyscans the channel in the time domain to determine the existence, timeoffset, and the signal strength of signals in the multiple pathenvironment. A searcher element is also called a search engine. Theoutput of the searcher element provides the information for ensuringthat demodulation elements are tracking the most advantageous paths.

[0031] A method and system for assigning demodulation elements to a setof available signals for both mobile stations and base stations isdisclosed in U.S. Pat. No. 5,490,165 entitled “DEMODULATION ELEMENTASSIGNMENT IN A SYSTEM CAPABLE OF RECEIVING MULTIPLE SIGNALS,” issuedFeb. 6, 1996, and assigned to the Assignee of the present.

[0032] When multiple mobiles transmit simultaneously, the radiotransmission from one mobile acts as interference to the other mobile'sradio transmission, thereby limiting throughput achievable on thereverse link (also called the uplink). For efficient capacityutilization on the reverse link, centralized scheduling at the basestation has been recommended in U.S. Pat. No. 5,914,950 entitled “METHODAND APPARATUS FOR REVERSE LINK RATE SCHEDULING,” issued Jun. 22, 1999,and U.S. Pat. No. 5,923,650 entitled “METHOD AND APPARATUS FOR REVERSELINK RATE SCHEDULING,” issued Jul. 13, 1999, both of which are assignedto the Assignee of the present.

[0033] In an exemplary embodiment, multi-level scheduling is performed.In an embodiment, multi-level scheduling comprises base station levelscheduling, selector level scheduling, and/or network level scheduling.

[0034] In an embodiment, a detailed design of a flexible schedulingalgorithm is based on fundamental theoretical principles that limitreverse-link system capacity, while using existing network parametersavailable or measured by a base station.

[0035] In an embodiment, base-station estimation of each mobile'scapacity contribution is based on measured signal-to-noise ratio (Snr)or pilot energy over noise plus interference ratio (Ecp/(Io+No)),collectively called (Ecp/Nt), given the current rate of transmission.Measurement of pilot Ecp/Nt from all fingers in multi-path scenario isdisclosed in U.S. application Ser. No. 10/011,519 entitled “METHOD ANDAPPARATUS FOR DETERMINING REVERSE LINK LOAD LEVEL FOR REVERSE LINK DATARATE SCHEDULING IN A CDMA COMMUNICATION SYSTEM,” filed Nov. 5, 2001, andassigned to the assignee of the present invention.

[0036] From the measurement of pilot Ecp/Nt at current rates ondifferent channels, capacity contribution of a mobile is estimated atnew rates on these channels.

[0037] In an embodiment, mobile requests for rate allocation areprioritized. A list of all mobiles that a scheduler is responsible forscheduling is maintained depending on which level the scheduling isperformed. In an embodiment, there is one list for all the mobiles.Alternatively, there are two lists for all mobiles. If the scheduler isresponsible for scheduling all the base stations a mobile has in itsActive Set, then the mobile belongs to a First List. A separate SecondList may be maintained for those mobiles that have a base station in theActive Set that the scheduler is not responsible for scheduling.Prioritization of mobile rate requests is based on various reported,measured or known parameters that maximize system throughput, whileallowing for mobile fairness as well as their importance status.

[0038] In an embodiment, Greedy Filling is used. In Greedy Filling, ahighest priority mobile obtains the available sector capacity. A highestrate that can be allocated to the mobile is determined as the highestrate that the mobile can transmit at. In an embodiment, the highestrates are determined based on measured SNR. In an embodiment, thehighest rates are determined based on Ecp/Nt. In an embodiment, thehighest rates are determined based also on limiting parameters. In anembodiment, the highest rate is determined by a mobile's bufferestimate. The choice of a high rate decreases the transmission delaysand decreases interference that the transmitting mobile observes.Remaining sector capacity can be allocated to the next lower prioritymobile. This methodology helps in maximizing the gains due tointerference reduction while maximizing the capacity utilization.

[0039] By the choice of different prioritization functions, the GreedyFilling algorithm can be tuned to the conventional round-robin,proportionally fair or most unfair scheduling based on a specified costmetric. Under the class of scheduling considered, the above method helpsaid maximum capacity utilization.

[0040] The mobile station initiates a call by transmitting a requestmessage to the base station. Once the mobile receives a channelassignment message from base station, it can use logical dedicatedchannel for further communication with the base-station. In a scheduledsystem, when the mobile station has data to transmit, it can initiatethe high-speed data transmission on the reverse link by transmitting arequest message on the reverse link.

[0041] Rate request and rate allocation structure currently specified inIS 2000 Release C is considered. However, it would be apparent to thoseskilled in the art that the scope of the design is not limited to IS2000. It would be apparent to those skilled in the art, that embodimentsmay be implemented in any multiple access system with a centralizedscheduler for rate allocation.

[0042] Mobile Station Procedures

[0043] In an embodiment, mobile stations (MS) at least support thesimultaneous operation of the following channels:

[0044] 1. Reverse Fundamental Channel (R-FCH)

[0045] 2. Reverse Supplemental Channel (R-SCH)

[0046] Reverse Fundamental Channel (R-FCH): When a voice-only MS has anactive voice-call, it is carried on the R-FCH. For data-only MS, R-FCHcarries signaling and data. Exemplary R-FCH channel frame size, coding,modulation and interleaving are specified in TIA/EIA-IS-2000.2, “MobileStation-Base Station Compatibility Standard for Dual-Mode WidebandSpread Spectrum Cellular System,” June, 2002.

[0047] In an exemplary embodiment, R-FCH at a null rate is used forouter-loop power control (PC), when an MS is not transmitting voice,data or signaling on R-FCH. Null rate means a lowest rate. R-FCH at alowest rate may be used to maintain outer-loop power control even whenthere is no transmission on R-SCH.

[0048] Reverse Supplemental Channel (R-SCH): The MS supports one R-SCHfor packet data transmissions in accordance with an embodiment. In anexemplary embodiment, the R-SCH uses rates specified by radioconfiguration (RC3) in TIA/EIA-IS-2000.2.

[0049] In an embodiment where only single data channel (R-SCH) issupported, the signaling and power control can be done on a controlchannel. Alternatively, signaling can be carried over R-SCH andouter-loop PC can be carried on R-SCH whenever it is present.

[0050] In an embodiment, the following procedures are followed by mobilestations:

[0051] Multiple Channel Adjustment Gain

[0052] Discontinuous Transmission and Variable Supplemental AdjustmentGain

[0053] Overhead transmission of R-CQICH and other control channels

[0054] Closed-loop Power Control (PC) command

[0055] Rate request using a Supplemental Channel Request Mini Message(SCRMM) on a 5-ms R-FCH or a Supplemental Channel Request Message (SCRM)on a 20-ms R-FCH

[0056] Multiple Channel Adjustment Gain: When the R-FCH and the R-SCHare simultaneously active, multiple channel gain table adjustment asspecified in TIA/EIA-IS-2000.2 is performed to maintain correcttransmission power of the R-FCH. The traffic-to-pilot (T/P) ratios forall channel rate are also specified in the Nominal Attribute Gain tablein appendix A as Nominal Attribute Gain values. Traffic-to-pilot ratiomeans the ratio of traffic channel power to pilot channel power.

[0057] Discontinuous Transmission and Variable Supplemental AdjustmentGain: The MS may be assigned an R-SCH rate by a scheduler during eachscheduling period. When the MS is not assigned an R-SCH rate, it willnot transmit anything on the R-SCH. If the MS is assigned to transmit onthe R-SCH, but it does not have any data or sufficient power to transmitat the assigned rate, it disables transmission (DTX) on the R-SCH. Ifthe system allows it, the MS may be transmitting on the R-SCH at a ratelower than the assigned one autonomously. In an embodiment, thisvariable-rate R-SCH operation is accompanied by the variable rate SCHgain adjustment as specified in TIA/EIA-IS-2000.2. R-FCH T/P is adjustedassuming the received pilot SNR is high enough to support the assignedrate on R-SCH.

[0058] Overhead transmission of R-CQICH and other control channels: Adata-only MS transmits extra power on CQICH and/or other controlchannels at a CQICH-to-pilot (or control-to-pilot) (C/P) ratio withmulti-channel gain adjustment performed to maintain correct transmissionpower of the R-CQICH (or control channels). (C/P) value may be differentfor MS in soft-handoff from those not in soft handoff. (C/P) representthe ratio of total power used by the control channels to the pilot powerwithout multichannel gain adjustment.

[0059] Closed-loop Power Control (PC) command: In an embodiment, an MSreceives one PC command per power control group (PCG) at a rate of 800Hz from all base stations (BSs) in the MS's Active Set. A PCG is a 1.25ms interval on the Reverse Traffic Channel and the Reverse PilotChannel. Pilot power is updated by +−1 dB based on an “Or-of-Downs”rule, after combining of the PC commands from co-located BSs (sectors ina given cell).

[0060] Rate request is done with one of two methods. In a first method,rate request is performed using a Supplemental Channel Request MiniMessage (SCRMM) on a 5-ms R-FCH as specified in TIA/EIA-IS-2000.5.

[0061] Supplemental Channel Request Mini Message (SCRMM) on a 5-msR-FCH: In an embodiment, each SCRMM transmission is 24 bits (or 48 bitswith the physical layer frame overhead in each 5-ms FCH frame at 9.6kbps).

[0062] The MS sends the SCRMM in any periodic interval of 5 ms. If a5-ms SCRMM needs to be transmitted, the MS interrupts its transmissionof the current 20-ms R-FCH frame, and instead sends a 5-ms frame on theR-FCH. After the 5-ms frame is sent, any remaining time in the 20-msperiod on the R-FCH is not transmitted. The discontinued transmission ofthe 20-ms R-FCH is re-established at the start of next 20-ms frame.

[0063] In a second method, rate request is performed using aSupplemental Channel Request Message (SCRM) on a 20-ms R-FCH.

[0064] Depending on different embodiments, different information can besent on a request message. In IS2000, Supplemental Channel Request MiniMessage (SCRMM) or a Supplemental Channel Request Message (SCRM) is senton the reverse-link for rate request.

[0065] In an embodiment, the following information shall be reported bythe MS to the BS on each SCRM/SCRMM transmission:

[0066] Maximum Requested Rate

[0067] Queue Information

[0068] Maximum Requested Rate: It can be the maximum data rate an MS iscapable of transmitting at the current channel conditions leavingheadroom for fast channel variations. An MS may determine its maximumrate using the following equation:${R_{\max}\quad ({power})} = {\underset{R}{\arg \quad \max}\begin{Bmatrix}{R\text{:}\quad {{Pref}(R)}*{{NormAvPiTx}\left( {PCG}_{i} \right)}*} \\\left( {1 + \left( {T/P} \right)_{R} + {\left( {\left( {T/P} \right)_{9.6k} + {C/P}} \right)\left( \frac{{Pref}\left( {9.6k} \right)}{{Pref}(R)} \right)}} \right) \\{\leq {{{Tx}\left( \max \right)}/{Headroom\_ Req}}}\end{Bmatrix}}$ $\begin{matrix}{{{NormAvPiTx}\left( {PCG}_{i} \right)} = {{\alpha_{Headroom}\frac{{TxPiPwr}\left( {PCG}_{i} \right)}{{Pref}({Rassigned})}} +}} \\{{\left( {1 - \alpha_{Headroom}} \right) \times}} \\{{{{NormAvPiTx}\left( {PCG}_{i - 1} \right)},}}\end{matrix}$

[0069] where Pref(R) is the “Pilot Reference Level” value specified inthe Attribute Gain Table in TIA/EIA-IS-2000.2, TxPiPwr(PCG_(i)) is theactual transmit pilot power after power constraints on the MS side areapplied in case of power outage, and NormAvPiTx(PCG_(i)) is thenormalized average transmit pilot power. An MS may be more conservativeor aggressive in its choice of headroom and determination of maximumrequested rate depending on what is permitted by the BS.

[0070] In an embodiment, the MS receives grant information by one of thetwo following methods:

[0071] Method a: Enhanced supplemental channel assignment mini message(ESCAMM) from BS on 5-ms forward dedicated control channel (F-DCCH) withrate assignment for specified scheduling duration.

[0072] Method b: Enhanced supplemental channel assignment message(ESCAM) from BS on forward physical data channel (F-PDCH) with rateassignment for specified scheduling duration.

[0073] The assignment delays depend on the backhaul and transmissiondelays and are different depending on which method is used for rategrant. During the scheduled duration, the following procedures areperformed:

[0074] In an embodiment where R-FCH is used to transmit autonomous dataand for outer-loop PC, the MS transmits data at an autonomous rate of9600 bps if it has some data in its buffer. Otherwise, the MS sends anull R-FCH frame at a rate of 1500 bps.

[0075] The MS transmits at the assigned R-SCH rate in a given 20-msperiod if the MS has more data than can be carried on the R-FCH and ifthe MS has decided that it would have sufficient power to transmit atthe assigned rate (keeping headroom for channel variations). Otherwise,there is no transmission on the R-SCH during the frame or the MStransmits at a lower rate which satisfies the power constraint. The MSdecides that it has sufficient power to transmit on the R-SCH at theassigned rate R in a given 20-ms period Encode_Delay before thebeginning of that 20-ms period if the following equation is satisfied:${{Pref}(R)}*{{NormAvPiTx}\left( {PCG}_{i} \right)}{\quad{\left\lbrack {1 + \left( {T/P} \right)_{R} + {\left( {\left( {T/P} \right)_{R_{FCH}} + \left( {C/P} \right)} \right)\left( \frac{{Pref}\left( R_{FCH} \right)}{{Pref}(R)} \right)}} \right\rbrack < \frac{{Tx}\left( \max \right)}{Headroom\_ Tx}}}$

[0076] where Pref(R) is the “Pilot Reference Level” value specified inthe Attribute Gain Table in TIA/EIA-IS-2000.2, NormAvPiTx(PCG_(i)) isthe normalized average transmit pilot power, (T/P)_(R) is the traffic topilot ratio that corresponds to rate R and for all channel rates isspecified in the Nominal Attribute Gain table in appendix A as NominalAttribute Gain values, (T/P)_(RFCH) is the traffic to pilot ratio onFCH, (C/P) is the ratio of total power used by the control channels tothe pilot power without multichannel gain adjustment, T_(x)(max) is themaximum MS transmit power, and Headroom_Tx is the headroom the MS keepsto allow for channel variation.

[0077] The DTX determination is done once every frame, Encode_Delay PCGsbefore the R-SCH transmission. If the MS disables transmission on theR-SCH, it transmits at the following power: $\begin{matrix}{{{TxPwr}\left( {PCG}_{i} \right)} = {{PiTxPwr}\left( {PCG}_{i} \right)}} \\{\left\lbrack {1 + {\left( {\left( {T/P} \right)_{R_{FCH}} + \left( {C/P} \right)} \right)\left( \frac{{Pref}\left( R_{FCH} \right)}{{Pref}(R)} \right)}} \right\rbrack}\end{matrix}$

[0078] An MS encodes the transmission frame Encode_Delay before theactual transmission.

[0079] Base Station Procedures

[0080] In an embodiment, the BS performs the following essentialfunctions:

[0081] Decoding of R-FCH/R-SCH

[0082] Power control

[0083] Decoding of R-FCH/R-SCH

[0084] When there are multiple traffic channels transmitted by the MSsimultaneously, each of the traffic channels is decoded aftercorrelating with the corresponding Walsh sequence.

[0085] Power-control

[0086] Power control in a CDMA system is essential to maintain thedesired quality of service (QoS). In IS-2000, the RL pilot channel(R-PICH) of each MS is closed-loop power controlled to a desiredthreshold. At the BS, this threshold, called power control set point, iscompared against the received Ecp/Nt to generate power control command(closed-loop PC), where Ecp is the pilot channel energy per chip. Toachieve the desired QoS on the traffic channel, the threshold at the BSis changed with erasures on the traffic channel, and has to be adjustedwhen the data rate changes.

[0087] Set point corrections occur due to:

[0088] Outer-loop power control

[0089] Rate Transitions

[0090] Outer-loop power control: If the R-FCH is present, the powercontrol set point is corrected based on erasures of the R-FCH. If R-FCHis not present, the outer-loop PC is corrected based on erasures of somecontrol channel or R-SCH when the MS is transmitting data.

[0091] Rate Transitions: Different data rates on the R-SCH requiredifferent optimal set point of the reverse pilot channel. When data ratechanges on the R-SCH, the BS changes the MS's received Ecp/Nt by thePilot Reference Levels (Pref(R)) difference between the current and thenext R-SCH data rate. In an embodiment, the Pilot Reference Level for agiven data rate R, Pref(R), is specified in the Nominal Attribute GainTable in C.S0002-C. Since the closed-loop power control brings thereceived pilot Ecp/Nt to the set point, the BS adjusts the outer loopset point according to the next assigned R-SCH data rate:

Δ=Pref(Rnew)−Pref(Rold)

[0092] Set point adjustment is done ┌Δ┐ PCGs in advance of the new R-SCHdata rate if R_(new)>R_(old). Otherwise, this adjustment occurs at theR-SCH frame boundary. The pilot power thus ramps up or down to thecorrect level approximately in 1 dB step sizes of the closed loop asshown in FIG. 2.

[0093]FIG. 2 shows set point adjustment due to rate transitions on R-SCHin accordance with an embodiment. The vertical axis of FIG. 2 shows asetpoint of a base station controller (BSC) 202, a base transceiversubsystem (BTS) receiver pilot power 204, and the mobile station rate206. The MS rate is initially at R₀ 208. When the R-SCH data rateincreases, i.e., R1>R0 210, then the setpoint is adjusted according toP_(ref)(R₁)-P_(ref)(R₀) 212. When the R-SCH data rate decreases, i.e.,R2<R1 214, then the setpoint is adjusted according toP_(ref)(R₂)-P_(ref)(R₁) 216.

[0094] Scheduler Procedures

[0095] A scheduler may be collocated with the BSC, or BTS or at someelement in the network layer. A Scheduler may be multilevel with eachpart responsible for scheduling those MSs that share the lower layerresources. For example, the MS not in soft-handoff (SHO) may bescheduled by BTS while the MS in SHO may be scheduled by part of thescheduler collocated with BSC. The reverse-link capacity is distributedbetween BTS and BSC for the purpose of scheduling.

[0096] In an embodiment, the following assumptions are used for thescheduler and various parameters associated with scheduling inaccordance with an embodiment:

[0097] 1. Centralized Scheduling: The scheduler is co-located with theBSC, and is responsible for simultaneous scheduling of MSs acrossmultiple cells.

[0098] 2. Synchronous Scheduling: All R-SCH data rate transmissions aretime aligned. All data rate assignments are for the duration of onescheduling period, which is time aligned for all the MSs in the system.The scheduling duration period is denoted SCH_PRD.

[0099] 3. Voice and Autonomous R-SCH transmissions: Before allocatingcapacity to transmissions on R-SCH through rate assignments, thescheduler looks at the pending rate requests from the MSs and discountsfor voice and autonomous transmissions in a given cell.

[0100] 4. Rate Request Delay: The uplink request delay associated withrate requesting via SCRM/SCRMM is denoted as D_RL(request). It is thedelay from the time the request is sent to when it is available to thescheduler. D_RL(request) includes delay segments for over-the-airtransmission of the request, decode time of the request at the cells,and backhaul delay from the cells to the BSC, and is modeled as auniformly distributed random variable.

[0101] 5. Rate Assignment Delay: The downlink assignment delayassociated with rate assignment via ESCAM/ESCAMM is denoted asD_FL(assign). It is the time between the moment the rate decision ismade and the time the MS receiving the resultant assignment.D_FL(assign) includes backhaul delay from the scheduler to the cells,over-the-air transmission time of the assignment (based on methodchosen), and its decode time at the MS.

[0102] 6. Available Ecp/Nt Measurement: The Ecp/Nt measurement used inthe scheduler shall be the latest available to it at the last frameboundary. The measured Ecp/Nt is reported to the scheduler by the BTSreceiver periodically and so it is delayed for a BSC receiver.

[0103]FIG. 3 shows scheduling delay timing in accordance with anembodiment. The numbers shown are an example of typical numbers that maybe used by a BSC located scheduler though the actual numbers aredependent on backhaul delays and loading scenario of the deployedsystem.

[0104] The horizontal axis shows an SCH frame boundary 250, a last SCHframe boundary before a point A 252, a point A 254, a scheduling time256, and an action time 258. An Ec/Nt measurement window 260 is shownstarting at the SCH frame boundary 250 and ending at the last SCH frameboundary before point A 252. A time to last frame boundary 262 is shownfrom the last SCH frame boundary before point A 252 to point A 254. Atime to get information from the BTS to the BSC (6 PCGs) 264 is shownstarting at point A 254 and ending at the scheduling time 256.ActionTimeDelay (25 PCGs for Method a, 62 PCGs for Method b) 266 isshown to start at the scheduling time 256 and ending at the action time258.

[0105] Scheduling, Rate Assignment and Transmission Timeline

[0106] Given the assumed synchronous scheduling, most events related torequest, grant and transmission are periodic with period SCH_PRD.

[0107]FIG. 4 illustrates the timing diagram of a rate request,scheduling and rate allocation in accordance with an embodiment. Thevertical axes show the time lines for the BSC (scheduler) 402 and themobile 404. The MS creates an SCRMM 406 and sends a rate request to theBSC (scheduler) 408. The rate request is included in the SCRMM, which issent on R-FCH. The uplink request delay associated with rate requestingvia SCRM/SCRMM is denoted as D_RL(request) 410. A scheduling decision412 is made once every scheduling period 414. After the schedulingdecision 412, an ESCAM/ESCAMM 416 is sent on a forward channel from theBSC to the MS indicating a rate assignment 418. D_FL 420 is the downlinkassignment delay associated with rate assignment via ESCAM/ESCAMM.Turnaround time 422 is the time it takes to turnaround a rate request.It is the time from the rate request to rate assignment.

[0108] The following characterizes the timeline:

[0109] Scheduling Timing

[0110] Scheduled Rate Transmissions

[0111] MS R-SCH Rate Requests

[0112] Scheduling Timing: The scheduler operates once every schedulingperiod. If the first scheduling decision is performed at t_(i), then thescheduler operates at t_(i), t_(i)+SCH_PRD, t_(i)+2SCH_PRD . . .

[0113] Scheduled Rate Transmissions: Given that the MSs have to benotified of the scheduling decisions with sufficient lead-time, ascheduling decision has to be reached at Action Time of the ESCAM/ESCAMMmessage minus a fixed delay, ActionTimeDelay. Typical values ofActionTimeDelay for Methods a and b are given in Table 1.

[0114] MS R-SCH Rate Requests: R-SCH rate requests are triggered asdescribed below:

[0115] Before the beginning of each SCRM/SCRMM frame encode boundary,the MS checks if either of the following three conditions are satisfied:

[0116] 1. New data arrives and data in the MS's buffer exceeds a certainbuffer depth (BUF_DEPTH), and the MS has sufficient power to transmit ata non-zero rate; OR

[0117] 2. If the last SCRM/SCRMM was sent at time τ_(i), and the currenttime is greater than or equal to τ_(i)+SCH_PRD, and if the MS has datain its buffer that exceeds the BUF_DEPTH, and the MS has sufficientpower to transmit at a non-zero rate; OR

[0118] 3. If the last SCRM/SCRMM was sent at time τ_(i), and the currenttime is greater than or equal to τ_(i)+SCH_PRD, and if the currentassigned rate at the MS side based on received ESCAMM/ESCAM is non-zero(irrespective of the fact that the MS may not have data or power torequest a non-zero rate). “Current assigned rate” is the assigned rateapplicable for the current rate transmission. If no ESCAM is receivedfor the current scheduled duration, then the assigned rate is considered0. The rate assigned in the ESCAM/ESCAMM message with Action Time atsome later time takes effect after the Action Time.

[0119] If either of the above three conditions are satisfied, the MSsends a SCRMM/SCRM rate request.

[0120] In an embodiment, an SCRM/SCRMM request made at τ_(i) is madeavailable to the scheduler after a random delay at τ_(i)+D_RL(request)In another embodiment, different combinations of change in MS databuffer, change in MS maximum supportable rate and MS last request timeout may be used to determine the time when a rate request is sent.

[0121] Scheduler Description and Procedures

[0122] In an embodiment, there is one centralized scheduler element fora large number of cells. The scheduler maintains a list of all MSs inthe system and BSs in each MS's Active Set. Associated with each MS, thescheduler stores an estimate of an MS's queue size ({circumflex over(Q)}) and maximum scheduled rate (Rmax(s)).

[0123] The queue size estimate {circumflex over (Q)} is updated afterany of the following events happen:

[0124] 1. An SCRMM/SCRM is received: SCRMM/SCRM is received after adelay of D_RL(request). {circumflex over (Q)} is updated to:

[0125] {circumflex over (Q)}=Queue Size reported in SCRMM

[0126] If the SCRMM/SCRM is lost, the scheduler uses the previous (andthe latest) information it has.

[0127] 2. After each R-FCH and R-SCH frame decoding:

{circumflex over (Q)}={circumflex over(Q)}−Data_(tx)(FCH)+Data_(tx)(SCH)

[0128] where Data_(tx)(FCH) and Data_(tx)(SCH) is the data transmittedin the last R-FCH and R-SCH frame, respectively (if the frame is decodedcorrectly) after discounting the physical layer overhead and RLP layeroverhead.

[0129] 3. At the scheduling instant t_(i), scheduler estimates themaximum scheduled rate for the MS in accordance with an embodiment. Thebuffer size estimation is done as:

{circumflex over (Q)}(f)={circumflex over (Q)}−(R_(assigned)+9600)×┌ActionTimeDelay/20┐·20 ms+(( PL _(—) FCH _(—) OHD+SCH_(assigned) *PL _(—) SCH _(—) OHD)×(┌ActionTimeDelay/20┐)

[0130] The maximum scheduled rate is obtained as the minimum of themaximum power constrained rate and maximum buffer size constrained rate.Maximum power constrained rate is the maximum rate that can be achievedwith MS available power, and maximum buffer size constrained rate is themaximum rate such that the transmitted data is smaller or equal to theestimated buffer size. ${R_{\max}(s)} = {\min \begin{Bmatrix}{{R_{\max}({power})},} \\{\underset{\begin{matrix}R \\{R \leq {307.2{kbps}}}\end{matrix}}{\arg \quad \max}\left\{ R \middle| {{\hat{Q}(f)} \geq \left( {{\left( {R + 9600} \right) \times 20{ms}} - {{PL\_ FCH}{\_ OHD}}} \right.} \right.} \\\left. {\left. {{- {PL\_ SCH}}{\_ OHD}} \right) \times \left( {{{SCH\_ PRD}/20}{ms}} \right)} \right\}\end{Bmatrix}}$

[0131] where SCH_(Assigned) is an indicator function for the currentscheduling period, ${SCH}_{Assigned} = \left\{ \begin{matrix}1 & {{{if}\quad R_{assigned}} > 0} \\0 & {{{if}\quad R_{assigned}} = 0}\end{matrix} \right.$

[0132] R_(assigned) is the rate assigned on the R-SCH during the currentscheduling period and MS is supposed to transmit on the R-SCH until theActionTime of the next assignment. PL_FCH_OHD is physical layerfundamental channel overhead. PL_SCH_OHD is physical layer supplementalchannel overhead.

[0133] R_(max) (power) is the maximum rate that the MS can support givenits power limit. If the maximum requested rate by the MS is determinedaccording to an embodiment described herein, R_(max) (power) is themaximum rate reported in the last received SCRM/SCRMM message. If themaximum rate is determined according to a different embodiment, thescheduler can estimate R_(max) (power) from the reported information andMS capability to transmit at the assigned rate. For example, in anotherembodiment, the scheduler can estimate R_(max) (power) according to theequation below: ${R_{\max}\quad ({power})} = \begin{Bmatrix}{{\min \left\{ {{R({reported})},{R_{assigned} + 1}} \right\}};} & {{{if}\quad R_{tx}} = R_{assigned}} \\{{\min \left\{ {{R({reported})},{R_{assigned} - 1}} \right\}};} & {{{if}\quad R_{tx}} < R_{assigned}}\end{Bmatrix}$

[0134] R_(assigned) is the rate assigned during current schedulingperiod and R_(tx) is the rate transmitted on R-SCH during currentscheduling period. R_(assigned)+1 is rate one higher than what iscurrently assigned to the MS and R_(assigned)−1 is a rate one lower thanwhat is currently assigned to the MS. R(reported) is the maximum ratereported by the MS in rate request message like SCRM/SCRMM. The abovemethod may be used when R(reported) by the MS is not related to themaximum rate that MS is capable of transmitting at its current powerconstraints.

[0135] Arg max provides the maximum supportable rate by the scheduler.

[0136] Capacity Computation

[0137] The sector capacity at the jth sector is estimated from themeasured MSs' Sinrs. The Sinr is the average pilot-weighted combinedSinr per antenna. In an embodiment, the combining per power-controlgroup (PCG) is pilot-weighted combining over multiple fingers anddifferent antennas of the sector of interest. In an embodiment, thecombining per power-control group (PCG) is maximal ratio combining overmultiple fingers and different antennas. The combining is not overdifferent sectors in the case of a softer-handoff MS. The averaging canbe over the duration of a frame or it can be a filtered average over acouple of PCGs.

[0138] The following formula is used for estimating Load contribution toa sector antenna:${Load}_{j} = {\sum\limits_{j \in {{ActiveSet}{(i)}}}\quad \frac{{Sin}\quad {r_{j}\left( {R_{i},{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}{1 + {{Sin}\quad {r_{j}\left( {R_{i},{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}}}$

[0139] where Sinr_(j)(R_(i), E[R_(FCH)]) is the estimated Sinr if the MSis assigned a rate R_(i) on R-SCH and E[R_(FCH)] is the expected rate oftransmission on the R-FCH.

[0140] Let the measured pilot Sinr (frame average or filtered averagepilot Sinr averaged over two antennas) be (E_(cp)/N_(t))_(j), while itis assigned a rate of Rassign(SCH) on the R-SCH. Then, $\begin{matrix}{{{Sin}\quad {r_{j}\left( {R_{i},R_{FCH}} \right)}} = {\frac{{Pref}\left( R_{i} \right)}{{Pref}\left( {R_{assign}({SCH})} \right)}\left( {E_{cp}/N_{t}} \right)_{j}}} \\{\left\lbrack {1 + \left( {T/P} \right)_{R_{i}} + \left( {\left( {T/P} \right)_{R_{FCH}} + \left( {C/P} \right)} \right)} \right.} \\\left. \left( \frac{{Pref}\left( R_{FCH} \right)}{{Pref}\left( R_{i} \right)} \right) \right\rbrack\end{matrix}$

[0141] C/P can be an average (CQICH/Pilot) or a (Control-to-pilot)ratio.

[0142] For voice-only MSs, the following equation is used to estimatethe average received Sinr:${{Sin}\quad {r_{j}\left( {0,{E\left\lbrack {R_{FCH}(\upsilon)} \right\rbrack}} \right)}} = {\frac{\left( {E_{cp}/N_{t}} \right)_{j}}{{Pref}\left( {R_{assign}({SCH})} \right)} \times \left\lbrack {1 + {\begin{pmatrix}{{\left( {T/P} \right)_{9.6k}{P\left( {9.6k} \right)}} +} \\{{\left( {T/P} \right)_{4.8k}{P\left( {4.8k} \right)}} +} \\{{\left( {T/P} \right)_{2.7k}{P\left( {2.7k} \right)}} +} \\{{\left( {T/P} \right)_{1.5k}{P\left( {1.5k} \right)}} +} \\\left( {C/P} \right)\end{pmatrix}{{Pref}\left( {R_{FCH}^{\max} = {9.6k}} \right)}}} \right\rbrack}$

[0143] where P(R) is the probability of voice codec transmitting at thatrate. In another embodiment where a different voice codec with differentrate selections are used, the same equation is used with different ratesto estimate the expected Sinr due to voice transmission on R-FCH.

[0144] In a more generic formulation, with data-voice mobiles and nodata transmission on R-FCH, the voice-activity factor (ν) could be usedto estimate the average received Sinr as follows: $\begin{matrix}{{{Sin}\quad {r_{j}\left( {R_{i},{E\left\lbrack {R_{FCH}(\upsilon)} \right\rbrack}} \right)}} = \frac{{{Pref}\left( R_{i} \right)}\left( {E_{cp}/N_{t}} \right)_{j}}{{Pref}\left( {R_{assign}({SCH})} \right)}} \\{\left\lbrack {1 + \left( {T/P} \right)_{R_{i}} + \left( {\upsilon - 1 + {\upsilon \left( {T/P} \right)}_{R_{FCH}^{\max}}} \right)} \right.} \\\left. \left( \frac{{Pref}\left( R_{FCH}^{\max} \right)}{{Pref}\left( R_{i} \right)} \right) \right\rbrack\end{matrix}$

[0145] If the interference from neighboring sectors and average thermalnoise can be measured, a more direct measure of the capacity ofreverse-link called rise-over-thermal (ROT) can be obtained. Let theother-cell interference measured during previous transmission be denotedas I_(oc), thermal noise be N_(o), then the estimated ROT during thenext transmission can be estimated as${ROT}_{j} = {\frac{1}{\left( {1 - {Load}_{j}} \right)}{\left( {1 + {I_{oc}/N_{o}}} \right).}}$

[0146] If the scheduler is multi-level scheduler, with different levelsof the scheduler elements scheduling different MSs, the sector capacityneeds to be distributed across different scheduling elements. In anembodiment, where the scheduler has two scheduling elements, one at aBTS and the other at a BSC, let the estimated assigned Load at BSC beLoad_(j)(BSC) and the estimated assigned load at BTS be Load_(j)(BTS).Then,

Load_(j)(BSC)+Load_(j)(BTS)<=1−(1+I _(oc) /N _(o))/ROT(max).

[0147] Since the timing delay in scheduling at BSC is greater than BTS,estimated assigned load at BSC Load_(j)(BSC) can be known at BTS priorto scheduling at BTS. BTS scheduler prior to scheduling then hasfollowing constraint on the assigned load:

Load_(j)(BTS)<=1−(1+I _(oc) /N _(o))/ROT(max)−Load_(j)(BSC)

[0148] Scheduling Algorithm

[0149] The scheduling algorithm has the following characteristics:

[0150] a) scheduling least number of MS for increasing TDM gains,

[0151] b) CDM few users for maximum capacity utilization, and

[0152] c) prioritization of MS rate requests.

[0153] Prioritization of mobiles can be based on one or more of thevaried reported or measured quantities. A priority function thatincreases system throughput can have one or many of the followingcharacteristics:

[0154] The higher the measured pilot Ecp/Nt (normalized), the lower isthe mobile's priority. Instead of using a measured Ecp/Nt, a pilotEcp/Nt set-point that the base-station maintains for power controlouter-loop could be used. A lower Ecp/Nt (measured or set-point) impliesa better instantaneous channel and hence increased throughput if channelvariations are small.

[0155] For a mobile in SHO, pilot Ecp/Nt (measured or Set-point) can beweighted by an SHO factor to reduce the other-cell interference. Forexample, if average received pilot powers at all SHO legs is available,$\sum\limits_{k = 1}^{M}{{P_{i}^{rx}(k)}/{P_{i}^{rx}(j)}}$

[0156] can serve as an SHO factor, where P_(i) ^(rx) (k) is the averagereceived pilot power of the I^(th) mobile by the k^(th) base station inits Active Set, P_(i) ^(rx) (j) is the average received pilot power ofthe I^(th) mobile by the strongest, j^(th) base station in its ActiveSet, and M is the number of base stations in the mobile's Active Set(set of base stations in soft handoff with the mobile)

[0157] Higher the measured or estimated propagation loss, lesser is thepriority. Propagation Loss can be calculated from the measured receivedpilot power if the mobile periodically reports transmitted pilot powerin the request message like SCRM. Or otherwise, it can estimate whichmobile sees better propagation loss based on the reported strength ofthe FL Ecp/Nt

[0158] Velocity based priority function: If the base-station estimatedvelocity of a moving mobile using some velocity estimation algorithm,then stationary mobiles are given the highest priority, and middlevelocity mobiles are given the least priority.

[0159] Priority function based on above measured or reported parametersis an unfair priority function aimed at increasing the reverse-linksystem throughput. In addition, priority can be increased or decreasedby a cost metric that is decided by what grade of service a user isregistered for. In addition to the above, a certain degree of fairnesscould be provided by a Fairness factor. Two different kinds of Fairnessare described below:

[0160] Proportional Fairness (PF): PF is the ratio of maximum requestedrate to average achieved transmission rate. Thus, PF=R_(i) ^(req)/R_(i)^(alloc), where R_(i) ^(req) is the requested rate and R_(i) ^(alloc) isthe average rate allocated by the scheduler.

[0161] Round Robin Fairness (RRF): Round robin scheduling tries toprovide equal transmission opportunities to all the users. When a mobileenters the system, RRF is initialized to some value, say 0. Eachscheduling period the rate is not allocated to the mobile, RRF isincremented by one. Every time some rate (or the requested rate) isallocated to the mobile, RRF is reset to the initial value 0. Thisemulates the process where mobiles scheduled in the last schedulingperiod are last in the queue.

[0162] Fairness can be used together with Priority function to determinethe priority of the mobile in the Prioritization list. When Fairness isused alone to prioritize mobiles, it provides proportional fair orround-robin scheduling that is throughput optimal for reverse-link aswell as allowing multiple transmissions for full capacity utilization.

[0163] An embodiment which uses different aspects of previously definedpriority functions and proportional fairness may have a priority of thei^(th) user determined as:${w_{i} = {\frac{1}{{{Ecp}/{{Nt}_{i}({setpt})}}*{SHOfactor}} \cdot ({PF})^{\alpha}}},$

[0164] where the parameter α called Fairness factor can be used totrade-off fairness for system throughput. As α increases, fairness getsworse. Schedulers with higher α yield higher throughput.

[0165] Next we consider a particular embodiment where the schedulerwakes up every scheduling period and makes rate allocation decisionsbased on pending rate requests. The scheduling algorithm looks like theone described below.

[0166] Initialization: The MS rate requests are prioritized. Associatedwith each MS is a priority count PRIORITY. PRIORITY of an MS isinitialized to 0 in the beginning. When a new MS enters the system withsector j as the primary sector, its PRIORITY is set equal to themin{PRIORITY_(i), ∀i such that MS_(i) has sector j as the primarysector}

[0167] 1. Let the Load constraint be Load_(j)≦max Load, such that therise-over-thermal overshoot above a certain threshold is limited. Forthe calibration purposes, max Load value of 0.45 will be used by thescheduler. The capacity consumed due to pilot transmissions andtransmissions on fundamental channels (due to voice or data) is computedand the available capacity is computed as${{Cav}(j)} = {{\max \quad {Load}} - {\sum\limits_{j \in {ActiveSet}}\frac{{Sin}\quad {r_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}{1 + {{Sin}\quad {r_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}}}}$

[0168] where max Load is the maximum Load for which rise-over-thermaloutage criteria specified is satisfied.

[0169] MS rate requests are prioritized in decreasing order of theirPRIORITY. So MSs with highest PRIORITY are at the top of the queue. Whenmultiple MSs with identical PRIORITY values are at the top of the queue,the scheduler makes a equally-likely random choice among these MSs.

[0170] 2. Setk=1,

[0171] 3. The data-only MS at the kth position in the queue is assignedthe rate R^(k) given by$R_{k} = {\min \left\{ {{R_{\max}(s)},{\underset{R}{argmax}\begin{bmatrix}{R{{{Cav}(j)} - \frac{{Sin}\quad {r_{j}\left( {R,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}{1 + {{Sin}\quad {r_{j}\left( {R,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}} +}} \\{{\frac{{Sin}\quad {r_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}{1 + {{Sin}\quad {r_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}} \geq 0};{\forall{j \in {{ActiveSet}(k)}}}}\end{bmatrix}}} \right\}}$

[0172] The available capacity is updated to: $\begin{matrix}{{{Cav}(j)} = {{{Cav}(j)} - \frac{{Sin}\quad {r_{j}\left( {R_{k},{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}{1 + {{Sin}\quad {r_{j}\left( {R_{k},{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}} +}} \\{{\frac{{Sin}\quad {r_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}{1 + {{Sin}\quad {r_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}};{\forall{j \in {{ActiveSet}(k)}}}}}\end{matrix}$

[0173] 4. If R_(max) ^(k)(s)>0 and R_(k)=0, increment PRIORITY of the MSOtherwise, do not change PRIORITY of the MS

[0174] 5. k=k+1; if k<total number of MSs in the list, Go to Step 3,otherwise, stop. TABLE 1 Baseline specific parameters Typical ParameterValues Comments Headroom_Req 5 dB Conservative rate request Keeps powerheadroom for long- term channel variation Reduces DTX on R-SCHHeadroom_Tx 2 dB Reduces probability of power outage during the durationof R- SCH transmission Average Tx Power Filter 1/16 Normalized Averagetransmit Coefficient α_(Headroom) pilot power is computed as filteredversion over several PCGs ActionTimeDelay 31.25 ms Based on the expectedESCAMM (Method a) delay, including the 2 PCG MS encoding delayActionTimeDelay  77.5 ms Based on the expected ESCAM (Method b) delay onF-PDCH at the primary sector Geometry of −5 dB. This includes the 2 PCGMS encoding delay

[0175] It would be apparent to those skilled in the art that othervalues can be used for the parameters in table 1. It would also beapparent to those skilled in the art that more or less parameters may beused for a particular implementation.

[0176]FIG. 5 is a flowchart of a scheduling process in an embodiment. Inan embodiment, a mobile i and a mobile j send a request rate to ascheduler in step 300. Alternatively, a mobile i and a mobile j send arequest rate to a scheduler in step 310.

[0177] In step 300, the scheduler creates a list of mobiles (Mi) that itwill schedule. Then, the scheduler creates a list of base stations(BTSs) the scheduler is responsible for scheduling. Also, the schedulercreates a list of mobiles that are not in the list of base stations thescheduler is responsible for scheduling and that are in soft handoff(SHO) with base stations the scheduler is responsible for scheduling(U_(i)). The flow of control goes to step 302.

[0178] The BTS supplies the scheduler with a reported DTX by a mobile.In step 302, a check is made to determine whether a mobile, which isscheduled, reported a DTX, in which case resources can be reallocatedfrom the scheduled mobile if a_(i) is less than the last schedule timeminus 1 plus a schedule period. ai is current time. t_(i) is the lastscheduled time. In step 302, the resources are reallocated before thescheduled time. The rate of the scheduled mobile is reset and theavailable capacity is reallocated to other requesting mobiles. In step306, a check is made to determine whether the current time has reached ascheduled point. If the current time has not reached a scheduled point,then the flow of control goes to step 302. If the current time hasreached a scheduled point, then the flow of control goes to step 308.

[0179] In step 308, the scheduler is supplied by the BTSs with anestimate of loc and piolot Ec/Nt of {M_(i)}union{U_(i)}. The capacity ofeach Bi is initialized given the loc estimates. For each Bi, subtractingfrom the available capacity, the voice users contribution to capacitygiven voice activity and autonomous transmission on R-FCH/R-DCCH. Themeasurement used for the amount subtracted is the pilot Ecp/Nt. Also foreach Bi, subtracted from the available capacity is the expectedcontribution by {Ui}. Then, the flow of control goes to step 310.

[0180] In step 310, pilot Ec/Nt of {M_(i)} and set-point and Rx pilotpower are provided to the scheduler and are used by a prioritizationfunction. The mobile rate requests are prioritized in a prioritizationqueue. In an embodiment, a prioritization function is used in whichmeasured and reported information is used. In an embodiment, aprioritization function provides for fairness. The flow of control goesto step 312.

[0181] In step 312, a maximum rate is assigned to a highest prioritymobile such that a capacity constraint of all BSs in soft handoff is notviolated. The maximum rate is the maximum rate supported by the highestpriority mobile. The highest priority mobile is placed last in theprioritization queue. The available capacity is updated by subtractingthe mobile contribution to capacity at an assigned maximum rate. Theflow of control goes to step 314.

[0182] In step 314, a check is made to determine whether all the mobilesin the {Mi} list have been scanned. If all the mobiles in the {Mi} listhave not been scanned, then the flow of control goes to step 312. If allthe mobiles in the {Mi} list have been scanned, then the flow of controlgoes to step 302.

[0183] Those of skill in the art would understand that method stepscould be interchanged without departing from the scope of the invention.Those of skill in the art would also understand that information andsignals might be represented using any of a variety of differenttechnologies and techniques. For example, data, instructions, commands,information, signals, bits, symbols, and chips that may be referencedthroughout the above description may be represented by voltages,currents, electromagnetic waves, magnetic fields or particles, opticalfields or particles, or any combination thereof.

[0184] Those of skill in the art would understand that information andsignals may be represented using any of a variety of differenttechnologies and techniques. For example, data, instructions, commands,information, signals, bits, symbols, and chips that may be referencedthroughout the above description may be represented by voltages,currents, electromagnetic waves, magnetic fields or particles, opticalfields or particles, or any combination thereof.

[0185]FIG. 6 is a block diagram of a BS 12 in accordance with anembodiment. On the downlink, data for the downlink is received andprocessed (e.g., formatted, encoded, and so on) by a transmit (TX) dataprocessor 612. The processing for each channel is determined by the setof parameters associated with that channel, and in an embodiment, may beperformed as described by standard documents. The processed data is thenprovided to a modulator (MOD) 614 and further processed (e.g.,channelized, scrambled, and so on) to provide modulated data. Atransmitter (TMTR) unit 616 then converts the modulated data into one ormore analog signals, which are further conditions (e.g., amplifies,filters, and frequency upconverts) to provide a downlink signal. Thedownlink signal is routed through a duplexer (D) 622 and transmitted viaan antenna 624 to the designated MS(s).

[0186]FIG. 7 is a block diagram of an MS 106 in accordance with anembodiment. The downlink signal is received by an antenna 712, routedthrough a duplexer 714, and provided to a receiver (RCVR) unit 722.Receiver unit 722 conditions (e.g., filters, amplifies, and frequencydownconverts) the received signal and further digitizes the conditionedsignal to provide samples. A demodulator 724 then receives and processes(e.g., descrambles, channelizes, and data demodulates) the samples toprovide symbols. Demodulator 724 may implement a rake receiver that canprocess multiple instances (or multipath components) of the receivedsignal and provide combined symbols. A receive (RX) data processor 726then decodes the symbols, checks the received packets, and provides thedecoded packets. The processing by demodulator 724 and RX data processor726 is complementary to the processing by modulator 614 and TX dataprocessor 612, respectively.

[0187] On the uplink, data for the uplink, pilot data, and feedbackinformation are processed (e.g., formatted, encoded, and so on) by atransmit (TX) data processor 742, further processed (e.g., channelized,scrambled, and so on) by a modulator (MOD) 744, and conditioned (e.g.,converted to analog signals, amplified, filtered, and frequencyupconverted) by a transmitter unit 746 to provide an uplink signal. Thedata processing for the uplink is described by standard documents. Theuplink signal is routed through duplexer 714 and transmitted via antenna712 to one or more BSs 12.

[0188] Referring back to FIG. 6, at BS 12, the uplink signal is receivedby antenna 624, routed through duplexer 622, and provided to a receiverunit 628. Receiver unit 628 conditions (e.g., frequency downconverts,filters, and amplifies) the received signal and further digitizes theconditioned signal to provide a stream of samples.

[0189] In the embodiment shown in FIG. 6, BS 12 includes a number ofchannel processors 630 a through 630 n. Each channel processor 630 maybe assigned to process the sample steam for one MS to recover the dataand feedback information transmitted on the uplink by the assigned MS.Each channel processor 630 includes a (1) demodulator 632 that processes(e.g., descrambles, channelizes, and so on) the samples to providesymbols, and (2) a RX data processor 634 that further processes thesymbols to provide the decoded data for the assigned MS.

[0190] Controllers 640 and 730 control the processing at the BS and theMS, respectively. Each controller may also be designed to implement allor a portion of the scheduling process. Program codes and data requiredby controllers 640 and 730 may be stored in memory units 642 and 732,respectively.

[0191] Those of skill would further appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the embodiments disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

[0192] The various illustrative logical blocks, modules, and circuitsdescribed in connection with the embodiments disclosed herein may beimplemented or performed with a general purpose processor, a digitalsignal processor (DSP), an application specific integrated circuit(ASIC), a field programmable gate array (FPGA) or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

[0193] The steps of a method or algorithm described in connection withthe embodiments disclosed herein may be embodied directly in hardware,in a software module executed by a processor, or in a combination of thetwo. A software module may reside in RAM memory, flash memory, ROMmemory, EPROM memory, EEPROM memory, registers, hard disk, a removabledisk, a CD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such the processorcan read information from, and write information to, the storage medium.In the alternative, the storage medium may be integral to the processor.The processor and the storage medium may reside in an ASIC. The ASIC mayreside in a user terminal. In the alternative, the processor and thestorage medium may reside as discrete components in a user terminal.

[0194] The previous description of the disclosed embodiments is providedto enable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for estimating capacity used on areverse link, comprising: measuring a plurality of signal-to-noiseratios at a station for a plurality of rates; determining sector loadbased on the measured plurality of signal-to-noise ratios, an assignedtransmission rate, and an expected transmission rate; and estimatingcapacity on the reverse link based on the sector load.
 2. The method ofclaim 1, wherein the measured plurality of signal-to-noise ratios isaveraged.
 3. The method of claim 2, wherein the measured plurality ofsignal-to-noise ratios is averaged over a duration of a frame.
 4. Themethod of claim 2, wherein the measured plurality of signal-to-noiseratios is averaged over a plurality of pilot control groups.
 5. Themethod of claim 2, wherein the station is a base station.
 6. A method ofestimating load contribution to a sector antenna, comprising: assigninga transmission rate R_(i) on a first communication channel; determiningan expected rate of transmission E[R] on a second communication channel;estimating a signal-to-noise ratio of a station for the assignedtransmission rate R_(i) on the first communication channel and theexpected rate of transmission E[R] on a second communication channel;and estimating the load contribution based on the estimatedsignal-to-noise ratio.
 7. The method of claim 6, wherein the loadcontribution to a sector antenna j is estimated based on:${Load}_{j} = {\sum\limits_{j \in {{ActiveSet}{(i)}}}{\frac{{Sin}\quad {r_{j}\left( {R_{i},{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}{1 + {{Sin}\quad {r_{j}\left( {R_{i},{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}}.}}$


8. The method of claim 7, wherein the first communication channel is areverse link supplemental channel and the second communication channelis a reverse link fundamental channel.
 9. A method for estimatingcapacity available to schedule, comprising: measuring other-cellinterference during a previous transmission (I_(oc)); determiningthermal noise (N_(o)); determining sector load (Load_(j)); anddetermining rise-over-thermal (ROT_(j)) based on the ratio of themeasured other-cell interference over thermal noise, and based on thesector load.
 10. The method of claim 9, wherein the rise-over-thermal(ROT_(j)) is determined as${ROT}_{j} = {\frac{1}{\left( {1 - {Load}_{j}} \right)}{\left( {1 + {I_{oc}/N_{o}}} \right).}}$


11. A method of distributing sector capacity across a base station (BS)and a base station controller (BSC), comprising: measuring other-cellinterference during a previous transmission (I_(oc)); determiningthermal noise (N_(o)); determining a maximum rise-over-thermal(ROT(max)); determining an estimated assigned load at the BSC(Load_(j)(BSC)); and determining a sector capacity distributed to thebase station based on the ratio of the measured other-cell interferenceover thermal noise, the maximum rise-over-thermal, and the estimatedassigned load at the BSC.
 12. The method of claim 11, wherein the sectorcapacity distributed to the base station is determined such that:Load_(j)(BTS)<=1−(1+I _(oc) /N _(o))/ROT(max)−Load_(j)(BSC).
 13. Amethod of determining priority of a station, comprising: determiningpilot energy over noise plus interference ratio (Ecp/Nt); determining asoft handoff factor (SHOfactor); determining a fairness value (F);determining a proportional fairness value (PF); determining a fairnessfactor α; and determining priority of a station based on the pilotenergy over noise plus interference ratio, the soft handoff factor, thefairness value, and the fairness factor α.
 14. The method of claim 13,wherein determining the soft handoff factor is based on average receivedpilot powers.
 15. The method of claim 13, wherein the fairness value isa proportional fairness value.
 16. The method of claim 13, wherein thefairness value is a round robin fairness value.
 17. The method of claim15, wherein determining the proportional fairness value is based on aratio of a maximum requested rate to an average transmission rate. 18.The method of claim 17, wherein determining priority of station w_(i) isbased on:$w_{i} = {\frac{1}{{Ecp}/{{Nt}_{i}\left( {SHOfactor} \right.}} \cdot {({PF})^{\alpha}.}}$


19. An apparatus for estimating capacity used on a reverse link,comprising: means for measuring a plurality of signal-to-noise ratios ata station for a plurality of rates; means for determining sector loadbased on the measured plurality of signal-to-noise ratios, an assignedtransmission rate, and an expected transmission rate; and means forestimating capacity on the reverse link based on the sector load.
 20. Anapparatus for estimating load contribution to a sector antenna,comprising: means for assigning a transmission rate R_(i) on a firstcommunication channel; means for determining an expected rate oftransmission E[R] on a second communication channel; means forestimating a signal-to-noise ratio of a station for the assignedtransmission rate R_(i) on the first communication channel and theexpected rate of transmission E[R] on a second communication channel;and means for estimating the load contribution based on the estimatedsignal-to-noise ratio.
 21. A station, comprising: an antenna forreceiving and transmitting a plurality of signals; a receiver coupled tothe antenna, the receiver receives the plurality of receive signals; acontroller coupled to the receiver, the controller measures a pluralityof signal-to-noise ratios for a plurality of rates; determines sectorload based on the measured plurality of signal-to-noise ratios, anassigned transmission rate, and an expected transmission rate; andestimates capacity on the reverse link based on the sector load; and atransmitter coupled to the controller, the transmitter conditions thecapacity estimation for transmission.
 22. The station of claim 21,wherein the station is a base station.
 23. A method of estimating loadcontribution to a sector antenna, comprising: an antenna for receivingand transmitting a plurality of signals; a receiver coupled to theantenna, the receiver receives the plurality of receive signals; acontroller coupled to the receiver, the controller assigns atransmission rate R_(i) on a first communication channel; determines anexpected rate of transmission E[R] on a second communication channel;estimates a signal-to-noise ratio of a station for the assignedtransmission rate Ri on the first communication channel and the expectedrate of transmission E[R] on a second communication channel; andestimates the load contribution based on the estimated signal-to-noiseratio; and a transmitter coupled to the controller, the transmitterconditions the load contribution estimation for transmission.
 24. Acomputer-readable medium embodying a program of instructions executableby a processor to perform a method of estimating capacity used on areverse link, comprising: measuring a plurality of signal-to-noiseratios at a station for a plurality of rates; determining sector loadbased on the measured plurality of signal-to-noise ratios, an assignedtransmission rate, and an expected transmission rate; and estimatingcapacity on the reverse link based on the sector load.
 25. Acomputer-readable medium embodying a program of instructions executableby a processor to perform a method of estimating load contribution to asector antenna, comprising: assigning a transmission rate R_(i) on afirst communication channel; determining an expected rate oftransmission E[R] on a second communication channel; estimating asignal-to-noise ratio of a station for the assigned transmission rateR_(i) on the first communication channel and the expected rate oftransmission E[R] on a second communication channel; and estimating theload contribution based on the estimated signal-to-noise ratio.